Radiological and thermal characteristics of CASTOR RBMK-1500 and CONSTOR RBMK-1500 casks for spent nuclear fuel storage at Ignalina Nuclear Power Plant

Abstract

The main characteristics, such as temperatures of the fuel rod cladding and cask surface, dose rates at the surface and at the some distance for CASTOR RBMK-1500 and CONSTOR RBMK-1500 casks loaded with spent nuclear fuel are presented. These casks are used for an interim dry storage of spent nuclear fuel at Ignalina Nuclear Power Plant. Numerical modeling (calculation of the equivalent dose rates, activities of nuclides, etc.) and experimental measurements of the equivalent dose and gamma spectrum on the cask surface at the dry storage facility were performed for assessment of radiation characteristics. Temperatures were evaluated using only numerical modeling. Rather good agreement between experimentally determined and calculated dose rates for CASTOR RBMK-1500 and CONSTOR RBMK-1500 casks was obtained. Also it was revealed that maximum fuel rod cladding temperature is higher for CONSTOR RBMK-1500 cask, but never exceeds the maximum allowable value. The cask surface temperatures are similar for both cask types.

Modeling of decay heat removal from CONSTOR RBMK-1500 casks during long-term storage of spent nuclear fuel

“…This is because the solar intensity on horizontal surfaces is higher than on the cask's vertical surfaces and due to the shadow effect of the neighboring casks. Figure 4 presents typical axial temperature distributions in the casks during cask storage from 5 to 300 years for warm and cold conditions including the data of a study [16] on cask storage for 5 and 50 years. As it is seen in Figure 4(a), the maximum temperature in summer time is recorded in the center of the fuel load.…”

“…The temperatures do not really change over the body of the cask at the same height because it has good conductivity characteristics. Figure 6 presents characteristics summarizing temperature distributions during the whole period of cask storage up to 300 years also considering the data from the study [16] on cask storage results after 5 and 50 years for summer (ambient temperature 37 °C) and winter (ambient temperature -42 °C) conditions. As it is seen from Figure 6(a), and as it has been already mentioned above, the fuel load temperatures in summer time change mostly during 50 years of storage.…”

“…In a study [16], using the ALGOR (USA) numerical modeling code, thermal results were obtained for CASTOR and CONSTOR non-ventilated casks for an interim storage of RBMK-1500 SNF for period of 50 years. Thermal regimes for CASTOR and CONSTOR casks at different storage conditions were provided.…”

“…A cask was modeled assuming it is at an open type storage facility in summer and winter conditions. The combined analysis also included the results [16] for interim storage up to 50 years. The analyses showed that the fuel load temperature decreases most significantly during the first 50 years of interim storage.…”

Comparison of Gamma and Neutron Dose Rate Variations with Time for Cast Iron and Metal–Concrete Casks Used for RBMK-1500 Spent Fuel Storage

“…In previous publications concerning the shielding analysis of cast iron and metalconcrete containers used for RBMK-1500 SF storage [6][7][8], radiation characteristics of spent fuel and resulting dose rates for these storage containers were estimated up to the planned storage time (50 years). A few papers provided comparisons between measured dose rates at ISFS-1 of Ignalina NPP and calculated dose rates for cast iron and metal-concrete containers [9][10][11].…”